Dye bleaching bath for the silver dye bleaching process

ABSTRACT

Color photographic images are produced by the silver dye bleaching process in which the bleaching is accelerated with a bleaching bath containing substituted 1,5-diazanaphthalenes as defined below.

United States Patent 1191 Hiinig et al.

[ DYE BLEACHING BATH FOR THE SILVER DYE BLEACHING PROCESS [75]inventors: Siegfried Hiinig, Wurzburg; Max

Heilmann, Cologne; Peter Bergthaller, Leichlingen, all of Germany 73 1'Assignee: Agfa-Gevaert Aktiengesellschaft,

Leverkusen, Germany 22 Filed: July 28,1971

211 App]. No.: 166,906

[30] Foreign Application Priority Data July 31, 1970 Germany P 20 38008.9

[52] US. Cl 96/53, 96/20 [51] Int. Cl G03c 7/00 [451 Aug. 28, 1973 [58]Field of Search 96/53, 73, 20

[56] References Cited UNIT ED STATES PATENTS 3,480,438 11/1969 Freytaget al 96/53 3,656,953 4/1972 Schlunke et a1. 96/53 PrimaryExaminer-Norman G. Torchin Assistant Examiner-R. L. SchillingAttorney-Arthur C. Connolly, Albert F. Bower et a1.

[57] ABSTRACT Color photographic images are produced by the silver dyebleaching process in which the bleaching is accelerated with a bleachingbath containing substituted 1 ,5- diazanaphthalenes as defined below.

7 Claims, 1 Drawing Figure DYE BLEACHING BATH FOR THE SILVER DYEBLEACHING PROCESS The present invention relates to a dye bleaching bathfor the silver dye bleaching process, which bath contains derivatives of1,5-diazanapthalene as bleaching catalysts.

In the known silver dye bleaching process, a photographic materialcomprising light-sensitive silver halide emulsion layers which containazo dyes is exposed to light and then developed and fixed in the usualmanner. A negative silver image of the original is obtained in theemulsion layers. The photographic material is then treated with a dyebleaching bath and, as the last stage of processing, with a silverbleaching bath or bleach fixing bath. A positive color image of theoriginal is obtained. The process is based on the bleaching of organicdyes, especially azo dyes, with finely divided silver, in this case thephotographically produced image silver, the extent of bleachingdepending on the quantity of silver present.

Successful bleaching of the dye in the course of the photographicprocess is essential for the economy of the process and the quality ofthe color images obtained. A particularly important factor is thatbleaching should be sufficiently rapid.

The known baths, which contain as their main components an inorganic ororganic acid and substances which form silver salts or silver complexes,generally bleach too slowly, so that it is necessary to use bleachingcatalysts at the same time. Heterocyclic nitrogen compounds are suitablefor this purpose, e.g., quinoline, isoquinoline or derivatives thereof,quinoxalines and azines such as phenazine or naphthazine. In spite ofthe use of bleaching catalysts, it is desirable to shorten the bleachingtime even further.

It is among the objects of the present invention to provide bleachingbaths for the silver dye bleaching process which enable sufficientlyrapid bleaching to be achieved, the rate depending on the quantity ofsilver present.

We now have found a bleaching bath for the silver dye bleaching process,which bath contains inorganic or organic acids, a substance which formssilver salts or silver complex salts, and a heterocyclic nitrogencompound as bleaching catalyst, said compound being a derivative of1,5-diazanaphthalene of the following formula:

n is 0,1 or 2.

The bleaching catalysts to be used according to the invention are veryhighly active even in relatively small concentrations. They are,therefore, considerably superior for this purpose to the knownunsubstituted l,5- diazanaphthalene.

The following are examples of suitable compounds:

1. 1,5-dimethyl-1,S-diazanaphthalenium-bismethylsulfate 2. 1,5-diethyl-1,5-diazanapthalenium-bis-ethylsulfate 3. 1 ,S-bis-m-sulfopropyl-l,S-diazanaphthalenium betaine 4.1,5-di-n-butyl-1,S-diazanaphthalenium-bis-butyl sulfate 5l-m-sulfopropyl betaine-5-methyl-1,5-

diazanaphthalenium methylsulfate.

The compounds which are to be used according to the invention areprepared by known methods. The simplest method is to start fromunsubstituted 1,5- diazanaphthalene and react this with a powerfulalkylating agent, e.g., with dimethyl sulfate, diethyl sulfate oralkyloxonium borofluorides or sultones.

The method of preparation of some compounds is described in detailbelow.

Compound 1 (as fluoborate) 10 mmol of 1,5-diazanaphthalene and 40 mmol(5.9 g) of trimethyloxonium fluoborate are together stirred in 50 ml ofanhydrous ethylene chloride for 20 hours. 5 ml of methanol are thenadded, and the reaction mixture is briefly stirred, suction filtered,washed with ethylene chloride and recrystallized from aqueous ethanol.The fluoborate analog of compound 1 is obtained in percent yield. Thedecomposition point is 280C. Compound 2 1.3 g of 1,5-diazanaphthaleneand 10 ml of diethyl sulfate are heated on a water bath for 12 hourswith exclusion of moisture. After cooling, the precipitate is removed bysuction filtration, pressed on clay and washed with acetone.Decomposition point above 170C.

Compound 3 1.3 g of 1,5-diazanaphthalene and 6.1 g of propane sultoneare heated to C for 5 hours. The mixture is then left' to cool anddigested with isopropanol. The residue is recystallized from water. Thecompound decomposes above 250C.

The other compounds are prepared similarly.

The bleaching catalysts according to the invention are added to thebleach bath in amounts of between 0.005 and 0.200 g/l.

The effect of the bath according to the invention is substantiallyindependent of the nature of the azo dye insofar as any given azo dye isbleached much more rapidly than with conventional baths. The bathaccording to the invention may, therefore, be used quite generally forthe silver dye bleaching process regardless of the nature of the dyeused. 5

The materials which are to be processed in the baths according to theinvention are prepared in a known manner. The azo dyes in the silverhalide emulsion layers may be e.g., those described in the followingpatent specifications:

German Pat. specifications Nos. 1,257,568; 1,246,404; 1,300,827 and1,284,299 and British Pat. specifications Nos. 1,134,394; 1,146,118;1,146,406 and 1,178,424(

The other stages of the process may also be carried out in the usualmanner, e.g., as follows:

1. Development 5 minutes in a bath of 1 g of pmethylamino phenol, 3 g ofhydroquinone, 13 g of anhydrous sodium sulfite, 1 g of sodium bromide,26 g of anhydrous sodium carbonate, made up to 1,000 ml with water.

2. Wash 5 minutes.

3. Fix 5 minutes in a bath of 200 g of sodium thiosulfate cryst. and 20g of potassium metabisulfite made up to 1,000 ml with water.

4. Wash 5 minutes.

5. Harden 5 minutes in a bath of 100 ml of 30 percent formalin and 2 gof sodium bicarbonate made up to 1,000 ml with water.

6. Wash 5 minutes.

7. Dye bleaching.

8. Wash 5 minutes.

9. Bleach fixing for 10 minutes in a bath of 26 g of tetrasodiumethylene diaminotetraacetate, 24 g anhydrous sodium carbonate 15 g ofiron (Ill) chloride, 13 g of anhydrous sodium sulfite, and 200 g ofsodium thiosulfate made up to 800 ml with water.

10. Wash 20 minutes.

The dye bleaching baths according to the invention have a pH of at themost 2 and preferably between and 1. The required pH range is adjustedby the addition of inorganic or organic acids, e.g., sulfuric acid,hydrohalic acids such as hydrochloric acid or hydrobromic acid,phosphoric acid, nitric acid, toluene sulfonic acid or naphthylenedisulfonic acid.

The silver salt forming agents used may be potassium halides or otheralkali metal halides, preferably iodides such as potassiumiodide.

The following may be used as silver complex forming agents:thiosemicarbazide or preferably thiourea or its derivatives.

Especially advantagous results are obtained by mixing potassium iodidewith thiourea.

The silver salt forming agents are advantageously used in quantities ofbetween 10 and 50 g/l and the complex forming agents in quantities offrom 10 to 200 EXAMPLE 1 A light-sensitive photographic material for thesilver dye bleaching process, consisting substantially of a redsensitivesilver bromide gelatin emulsion layer containing a cyan azo dye andmounted on a support, a greensensitive silver bromide gelatin emulsionlayer containing a magenta azo dye, a yellow filter layer and anuppermost blue-sensitive silver bromide gelatin emulsion layercontaining a yellow azo dye, is exposed to white light behind a greystep wedge. Six samples arethen processed as follows:

1. Development minutes in a bath of:

l g of p-methylamino phenol,

3 g of hydroquinone,

13 g of anhydrous sodium sulfite,

1 of sodium bromide, and

26 g of anhydrous sodium carbonate, made up to 1 litre with water; 2.Washing 5 minutes; 3. Hardening 5 minutes in a bath of:

60 ml of 30 percent formalin and 15 g of sodium bicarbonate made up to 1litre with water; 4. Washing 5 minutes.

The developed and hardened material is then treated in the followingstages, each sample being bleached in a different one of bleaching baths1 to 6 as described below;

5. Dye bleaching; 6. Washing 10 minutes.

Subsequent processing was then the same for all six sample strips.

7. Bleach fixing for 10 minutes in a bath of:

26 g of tetrasodium ethylene diaminotetraacetate,

24 g of anhydrous sodium carbonate 15 g of iron (III) chloride,

13 g of anhydrous sodium sulfite and 200 g of sodium thiosulfate made upto 800 ml with water; 8. Washing 20 minutes.

The various bleaching baths contain per litre:

Concentrated sulfuric acid 100 g Nal-l PO -H o 5 g Potassium iodide 10 gBleaching catalysts in the quantities shown in the following table.

The temperature of the dye bleaching bath is 30C, the

treatment time 10 minutes.

TABLE Catalyst bleaching bleaching molar bath quantity equivalents 10.075 g 1 1,5

diazanaphthalene 2 0.013 g l/l6 compound 1 3 0.0315 g l/8 compound 2 40.108 g l/2 compound 3 5 0.079 g 1/4 compound 4 6 0.018 g l/l2 compound5 The sensitometer strips obtained from all six samples are identical inappearance in spite of the considerable differences in concentration ofthe catalyst between comparison test 1 in which unsubstituted 1,5-diazanaphthalene was used and those in which bleaching baths (2) to (6)according to the invention were used.

It follows from the experiments that 1,5- diazanaphthalene, which isdifficult to obtain, can be converted nearly quantitatively by analkylating reaction into highly active products which, when used in thesame or equivalent quantities, enable the dye bleaching time to beconsiderably reduced or, when used for the same or even a shorter lengthof time, enable a considerable saving in bleaching catalyst to beobtained. In the case of the dimethylation product, this saving amountsto more than percent.

. EXAMPLE 2 A light-sensitive photographic material for the silver dyebleaching process, consisting substantially of a supported red-sensitivesilver bromide gelatin emulsion which contains a cyan azo dye, agreen-sensitive silver bromide gelatin emulsion layer containing amagenta azo dye, a yellow filterlayer and an uppermost bluesensitivesilver bromide emulsion layer containing a yellow azo dye, is exposed towhite light behind a grey step wedge. Eight samples are then processedas follows: 1. Development 5 minutes in a bath of:

l g of p-methylamino phenol 3 g of hydroquinone,

13 g of anhydrous sodium sulfite,

l g of sodium bromide and 26 g of anhydrous sodium carbonate made up to1 litre with water; 2. Washing 5 minutes; 3. Hardening 5 minutes in abath of:

60 ml of 30 percent formalin and 15 g of sodium bicarbonate, made up to1 litre with water; 4. Washing 5 minutes; 5. The developed and hardenedmaterial is then treated in the following stages, using the twobleaching baths (7) and (8) and bleaching being carried out at 30C 'for2%, 5, 7% and 10 minutes, each sample being subjected to a differentbleaching combination. 6. Washing 10 minutes; 7. Bleach fixing for 10minutes in a bath of:

26 g of tetrasodium ethylene diaminotetraacetate,

24 g of anhydrous sodium carbonate g of iron(lII) chloride,

13 g of anhydrous sodium sulfite, and

200 g of sodium thiosulphate, made up to 800 ml with water; 8. Washingminutes.

Bleaching baths (7) and (8) contain, per litre:

Concentrated sulfuric acid 100 g Sodium hypophosphite 5 g Potassiumiodide 10 g and:

' bleaching bath (7) 0.075 g of 1,5-diazanaphthalene bleaching bath (8)0.208 g of compound (1 The sensitometer strips obtained show that dyebleaching bath 8) is much more active than bath (7) which contains thesame molar quantity of catalyst. The sample which has been bleached for2% minutes in bath (8) is identical with the sample which has beenbleached for 7% minutes in bath (7). The sample which has been bleachedfor 5 minutes in bath (8) is much more strongly bleached than the samplewhich has been bleached for 10 minutes in bath (7).

EXAMPLE 3 The procedure is the same as described in Example 2 but usingdye bleaching baths (7) and (9). Bleaching bath (9) differs from bleachbath (8) only by its smaller quantity (0.075 g) of compound (l).

A comparison of the sensitometer strips obtained shows that the samplewhich has been bleached for 2 minutes in bath (9) is more stronglybleached than the sample which has been bleached for 5 minutes in bath(7).

The results of the comparison tests are represented in the figure. Thecurves show the y-value of the cyan part of the image as modified by theaction of the dye bleaching baths. The ordinate represents the densityand the abscissa the log 1.! value. The broken line curves 1, 2, 3 and 4show the efficiency of dye bleaching bath (7) acting for 2 5, 7 and 10minutes, respectively. The continuous line curves 1' to 4 represent theresults obtained after the same time with bleaching bath (9).

What we claim is:

1. In a catalyst-containing aqueous dye bleaching bath for the silverdye bleaching process, the improvement according to which the catalystis a substituted 1,5-diazanaphthalene of the following formula:

wherein R and R each represents a saturated or olefinically unsaturatedaliphatic group having up to five carbons, which may be substituted withhalogen, hydroxyl, alkoxy, carboxyl, sulfo or sulfato; and R and Rcombined may contain n acid groups X represents any photographicallyinert anion; and

n is 0, l or 2.

2. The combination of claim 1 in which the concentration of thebleaching catalyst is between 5 and 200 mg/ 1.

3. The combination of claim 1 in which the bath has a pH of between 0and l.

4. The combination of claim 1 in which the bath contains potassiumiodide as a silver-salt-forrning agent.

5. The combination of claim 1 in which the bath contains a thioureasilver-complex-forming agent.

6. in the process for the production of photographic images by means ofthe silver dye bleaching process, the improvement according to which thedye bleaching bath used is the bath of claim 1.

7. The combination of claim 2 in which the bath has a pl-l of between 0and l.

t t t t i

2. The combination of claim 1 in which the concentration of thebleaching catalyst is between 5 and 200 mg/1.
 3. The combination ofclaim 1 in which the bath has a pH of between 0 and
 1. 4. Thecombination of claim 1 in which the bath contains potassium iodide as asilver-salt-forming agent.
 5. The combination of claim 1 in which thebath contains a thiourea silver-complex-forming agent.
 6. In the processfor the production of photographic images by means of the silver dyebleaching process, the improvement according to which the dye bleachingbath used is the bath of claim
 1. 7. The combination of claim 2 in whichthe bath has a pH of between 0 and 1.